2.  What are the main benefits you get (or think you could get) from learning English through music? (e.g., vocabulary, pronunciation, listening skills, understanding culture/slang, motivation)

I think mainly motivation and different cultures. Of course some songs have many verbal uses that we usually cannot touch. But for vocabulary... it is of little use.

And English songs can also be an effective way to test yoru progress.

回復 @啊啊是誰都對：(Though sometimes that would create an illusion that "I'm learning English.")